This project will focus on creating a button-sized wearable sensor for monitoring personal exposure to both chemicals and particulate matter. This unprecedented capability will pair with physiological signal monitors to provide both environmental exposure and physiological response data. The data communication of the device will be designed such that it can be plugged into a smartphone or cloud computing data management system for easy access and analysis of the data by epidemiologists. Such a system will have an impact on the epidemiological study of the pollution exposure-response relationship, and eventually the prevention of pediatric asthma. The project will provide a wearable exposure sensor to address the challenges proposed by RFA-EB-15-002, Pediatric Research using Integrated Sensor Monitoring Systems (PRISMS): Sensor Development Projects for Asthma (U01). The sensor will be designed to pair with other physiological signal monitors, and plug into other data management system developed by PRISMS. The specific objectives of the project are to: 1) Develop a button-sized sensor that can monitor indoor and outdoor exposure of a child 24 hours a day. The initial target analytes include important potential asthma triggers, such as particulate matter, nitrogen dioxide, ozone, and formaldehyde, as well as temperature and humidity, but the sensor platform is expandable to allow inclusion of more analytes in the future. The sensor also includes an accelerometer chip to track whether the subjects actually wear the sensor as intended. 2) Pair the button-sized personal exposure sensor with physiological signal monitors, and develops seamless data communication with an Asthma Study App, and 3) validate the entire system via a small-scale pilot study. The project will bring together strengths in chemical sensors, particulate matter detectors, epidemiology, and digital health from different groups. In order to create a long lastin impact and benefit for the large environmental health study community and end users, the team will also work with industry collaborators to prepare for commercialization.